dmk9561 Posted August 15, 2009 Report Share Posted August 15, 2009 I've been driving my car for about a week now. On tuesday, it started having an occasional misfire, which has gotten worse. Yesterday, I changed all the plugs, which looked fine. That didn't make it better. It's had the plug wires replaced within the last 20,000 miles. When it's happening, the Service Engine Soon light is not on. going into diagnostic mode shows no current codes, and there is a "P044 HISTORY" which is rear O2 sensor lean, which it had when it was running ok. When it's happening, the car is obviously running rich and has smelly exhaust. Is it this O2 sensor? Link to comment Share on other sites More sharing options...
BostonETC97 Posted August 15, 2009 Report Share Posted August 15, 2009 You and I are pretty much fighting the same problem! I had a misfire in the morning, that improved quickly after warming up. Over a week or so, it got worse, to the point it was constant. I just changed all my plugs. That fixed the initial misfire, but now it has what feels to be a different misfire. I've covered all the basics (loose wires, vacuum, etc.), so I just ordered a new wire set for my newly installed plugs. I'll report back the results early next week once it arrives. Link to comment Share on other sites More sharing options...
Ranger Posted August 15, 2009 Report Share Posted August 15, 2009 Considering that you have a DTC for an O2 sensor, I'd start by replacing that. Link to comment Share on other sites More sharing options...
dmk9561 Posted August 16, 2009 Author Report Share Posted August 16, 2009 Considering that you have a DTC for an O2 sensor, I'd start by replacing that. I plan on replacing both of them soon. However, I think that it's a clogged fuel injector. On a whim, my dad suggested trying a bottle of injector cleaner since none of my preferred service garages are open on saturday. I put a bottle of Techron in and now it's better. Not perfect, but better than it was. I'll probably double up on the Techron and see if it gets better before I do anything else. I don't generally believe in bottles of stuff fixing problems, but maybe I got lucky this time. Link to comment Share on other sites More sharing options...
dmk9561 Posted August 19, 2009 Author Report Share Posted August 19, 2009 The Techron didn't cure the problem. I did the "Cylinder Balance Test" that I finally found the instructions to. The #2 cylinder made no change in engine speed and the others usually changed it by about 50 RPM. I'm going to check resistance on the #2 plug wire before I order an injector, but at least now I know that's where the problem is. Link to comment Share on other sites More sharing options...
Larry Posted August 21, 2009 Report Share Posted August 21, 2009 The Techron didn't cure the problem. I did the "Cylinder Balance Test" that I finally found the instructions to. The #2 cylinder made no change in engine speed and the others usually changed it by about 50 RPM. I'm going to check resistance on the #2 plug wire before I order an injector, but at least now I know that's where the problem is. If you have a timing light , hook this to each and every wire one at a time and look at the light, it will show the misfire plain as day if it is a plug or wire. GOOD LUCK Link to comment Share on other sites More sharing options...
BodybyFisher Posted August 21, 2009 Report Share Posted August 21, 2009 OBD1 does not set codes for misfiring, I dont believe Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
PAUL T Posted August 21, 2009 Report Share Posted August 21, 2009 I was going to suggest swapping out the coil on #2 but if it was the coil you would be having trouble with the coresponding cylinder on the coil with #2. Link to comment Share on other sites More sharing options...
dmk9561 Posted August 21, 2009 Author Report Share Posted August 21, 2009 I was going to suggest swapping out the coil on #2 but if it was the coil you would be having trouble with the coresponding cylinder on the coil with #2. Yeah, I already thought of that. I have not checked the wires yet because it's been raining the last few days and I've got a bad summer cold. I may go with the timing light idea-just put it on the wire out by the end and that tells if the wire is good, right? I don't have a timing light but a friend does. I've only ever owned one car with a distributor, and it's been 8 years since I sold it. Link to comment Share on other sites More sharing options...
BodybyFisher Posted August 21, 2009 Report Share Posted August 21, 2009 I was going to suggest swapping out the coil on #2 but if it was the coil you would be having trouble with the coresponding cylinder on the coil with #2. Yeah, I already thought of that. I have not checked the wires yet because it's been raining the last few days and I've got a bad summer cold. I may go with the timing light idea-just put it on the wire out by the end and that tells if the wire is good, right? I don't have a timing light but a friend does. I've only ever owned one car with a distributor, and it's been 8 years since I sold it. You can check your wires with an ohm meter also, record the readings and post them here, if you do Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
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